(1) Field of the Invention
The present invention relates to an image-forming process. More particularly, the present invention relates to an image-forming process in which a photosensitive toner is used and a positive image is formed according to the simultaneous voltage application/light exposure/transfer system.
(2) Description of the Prior Art
A process in which a photosensitive toner is used and an image is formed according to the simultaneous voltage application/light exposure/transfer system has already been known. For example, Japanese Patent Application Laid-Open Specification Nos. 98463/85 and 138566/85 disclose a process in which a photosensitive toner layer is formed on an electroconductive substrate, a transparent electrode is arranged to confront the toner layer, a bias voltage is applied so that the polarity of the toner-adhering substrate is reverse to the polarity of the toner and the polarity of the confronting electrode is the same as that of the toner, imagewise light exposure is carried out and an irradiated toner image is transferred to the confronting electrode to form an image.
However, according to this simultaneous voltage application/light exposure/transfer process, charges having a polarity reverse to the inherent polarity of the toner are injected into the photosensitive toner in the light-exposed region (bright region), and this toner charged with the reverse polarity is electrostatically attracted to the confronting electrode to form an image. Accordingly, the image formed by this process is a negative image, and theoretically, it is impossible to form a positive image on the side of the confronting electrode according to this process.
Furthermore, according to this process, various steps such as formation of the toner layer, erasion of charges from the toner, injection of charges into the toner and movement of toner particles from the electrode surface, for example, isolation (repulsion), are conducted in one zone, and therefore, the process is defective in that formation of a clear and sharp image with no fogging or no disturbance is difficult.
Moreover, in an ordinary electroscopic toner used for development in a photosensitive drum, in view of the charge quantity of the toner, the scattering property of the toner and the resolving power, the particle size has heretofore been adjusted within a certain range, for example, a range of from 5 to 20 .mu.m. Also in the field of the photosensitive toner, a particle size within this range has been similarly used.
However, in the image-forming process using a photosensitive toner, since the charged toner is light-exposed, there arises a problem quite different from the problem involved in an ordinary electroscopic toner. More specifically, since the photosensitive layer is composed of independent toner particles, obscuration of letters or fogging is often caused at the development and light exposure.
Various photoconductors and fixing resins have been proposed, but influences of the particle size characteristics on the photosensitivity, image density and image quality are almost unknown.